By the end of 2007, sexual transmission was responsible for more than half (52%) of the estimated 700,000 HIV infections in China and is expected to drive the country's future HIV epidemic. The prevalence of HIV among men who have sex with men (MSM) in China is on the rise (1%-10.4%). Efforts to control the emerging HIV epidemic among these men may be hindered by stigma and discrimination related to sexual orientation. Our work found that experiences of MSM stigma were highly prevalent among Chinese MSM and that those who had had such experiences were more likely to engage in unprotected sex with men or with both men and women. Similarly, studies of MSM in other countries have found a similar relationship between MSM stigma and sexual risk behaviors. However, the exact mechanisms by which such experiences of MSM stigma become linked to sexual risk behaviors remain largely unknown. Accordingly, we propose a three-phase study to identify the specific mechanisms by which MSM stigma affect sexual risk behaviors among MSM in Beijing, China. The proposed study will be guided by Major and O'Brien's identity threat model of stigma that connects stigma to mental and physical health outcomes via a stigma management mechanism. In Phase 1, we will explore the range of management strategies used to cope with MSM stigma via 30 in-depth qualitative interviews with MSM. In Phase 2, we will develop, using Phase 1 qualitative data and adapting existing quantitative scales, culturally-relevant measures of explanatory constructs of interest (e.g., MSM stigma management) to establish reliability and validity (N=170). In Phase 3, we will examine potential mediators (e.g., stigma management strategies, psychological distress, sexual contexts/situations) that explain how MSM stigma are linked to sexual risk for HIV with a respondent-driven sample of 500 MSM who will complete baseline and two follow-up assessments at 6 and 12 months. We will also conduct 20 in-depth qualitative individual interviews with a subset of men selected from the Phase-3 participants to examine the acceptability of potential intervention components to address the link between MSM stigma and HIV risk. This study will break new ground in our understanding of the influence of MSM stigma management strategies on sexual risk for HIV among MSM. It will also advance theoretical understanding of HIV risk by examining potential mechanisms through which MSM stigma and discrimination impact sexual risk. PUBLIC HEALTH SIGNIFICANCE: The proposed study addresses a critical public health issue by informing the next generation of HIV prevention strategies targeting those mechanisms of MSM stigmatization, which in turn may help prevent the worsening of the HIV epidemic among MSM throughout the world, including those in China.